The $z \sim 2$ $\rm{[O\ III]}$ Luminosity Function of Grism-selected Emission-line Galaxies

TL;DR

This study measures the [O III] luminosity function of galaxies at z~2 using HST grism data, providing insights for upcoming missions and a new star formation rate calibration.

Contribution

It presents the first detailed [O III] luminosity function for z~2 galaxies selected via HST grism, informing future survey strategies and galaxy evolution models.

Findings

Grism-selected galaxies account for about half of the star formation at z~2.

Provides a calibrated relation between [O III] luminosity and star formation rate.

Offers predictions for galaxy counts in Euclid and Roman surveys.

Abstract

Upcoming missions such as Euclid and the Nancy Grace Roman Space Telescope (Roman) will use emission-line selected galaxies to address a variety of questions in cosmology and galaxy evolution in the $z>1$ universe. The optimal observing strategy for these programs relies upon knowing the number of galaxies that will be found and the bias of the galaxy population. Here we measure the $\rm{[O\ III]}\ \lambda 5007$ luminosity function for a vetted sample of 1951 $m_{\rm J+JH+H} < 26$ galaxies with unambiguous redshifts between $1.90 < z < 2.35$, which were selected using HST/WFC3 G141 grism frames made available by the 3D-HST program. These systems are directly analogous to the galaxies that will be identified by the Euclid and Roman missions, which will utilize grism spectroscopy to find $\rm{[O\ III]}\ \lambda 5007$-emitting galaxies at $0.8 \lesssim z \lesssim 2.7$ and $1.7 \lesssim z \lesssim 2.8$, respectively. We interpret our results in the context of the expected number counts for these upcoming missions. Finally, we combine our dust-corrected $\rm{[O\ III]}$ luminosities with rest-frame ultraviolet star formation rates to present a new calibration of the SFR density associated with $1.90 < z < 2.35$ $\rm{[O\ III]}$-emitting galaxies. We find that these grism-selected galaxies contain roughly half of the total star formation activity at $z\sim2$.